Semiconductor dice are being fabricated with increasing numbers of integrated circuits. As circuit integration increases, the sizes of semiconductor components are becoming smaller. Bare dice and chip scale packages can be only millimeters in length, and fractions of a millimeter in thickness. In addition, the external contacts on the components are becoming smaller and more closely spaced. For example, for fine ball grid array (FGBA) components, external contact balls can have a diameter as small as about 0.127 mm (0.005 inch), and a center to center pitch as small as about 0.228 mm (0.008 inch).
Typically, these types of components are tested using test carriers that mount to a test board. Exemplary test carriers are described in U.S. Pat. No. 5,844,418 to Wood et al.; U.S. Pat. No. 5,815,000 to Farnworth et al.; and U.S. Pat. No. 5,783,461 to Hembree.
As the components and external contacts on the components become smaller, making temporary electrical connections with the components for testing becomes more difficult. The test carrier includes an interconnect having contacts that make the temporary electrical connections with the external contacts on the components. In addition, the test carrier include a force applying mechanism that applies a biasing force for biasing the component against the interconnect. An exemplary force applying mechanism includes a biasing member, such as a metal or elastomeric spring for applying the biasing force, and a clamp or latch plate for securing the biasing member to a base of the carrier.
During assembly of the component into the carrier, the external contacts on the component are aligned with the contacts on the interconnect, and then placed in electrical contact therewith. One method of alignment is with an optical alignment system, as described in U.S. Pat. No. 5,634,267 to Wood et al. Another method of alignment is with a mechanical alignment system, as described in U.S. Pat. No. 5,559,444 to Farnworth et al.
Also during assembly of the carrier, the force applying member is attached to the base. One problem that occurs with the assembly of this type of carrier, is that although the component and the interconnect may be initially aligned, the force applying mechanism and carrier base may be misaligned. This misalignment can cause the contacts on the component and the interconnect to become misaligned, or can cause a shear load to be placed between the component and the interconnect. With small closely spaced contacts, any misalignment or loading can adversely affect, or prevent, the temporary electrical connections between the component contacts and the interconnect contacts.
One method for avoiding misalignment and loading by the force applying mechanism is disclosed in U.S. Pat. No. 5,739,050 to Farnworth. This method employs an assembly tool having a slide mechanism that allows the force applying mechanism to freely slide and self center relative to the base of the carrier. However, this method requires an assembly tool which may not be compatible with some assembly systems, or with some manual assembly techniques.
In addition to being misaligned during assembly, the force applying member can also move following assembly, causing misalignment or loading of the contacts. For example, the assembled test carriers must be transported and also loaded onto test boards, and can be bumped during these procedures. It would be desirable to provide a test carrier with a force applying member that can be aligned with the base during assembly of the carrier, and protected from movement following assembly of the carrier.
In addition to the force applying mechanism, the test carrier can also include terminal contacts on the carrier base, which are adapted for electrical connection to the test board. The terminal contacts typically comprise pins or contact balls. During assembly and handling of the carriers, the terminal contacts are unprotected, and subject to bending and deformation by other equipment. Bending and deformation is a particular problem during placement of the terminal contacts into engagement with mating contacts on the test board. It would be desirable to provide a test carrier with a protector for protecting the terminal contacts, and for aiding in the alignment of the terminal contacts to mating contacts on a test board.